Grand Lake St Marys Water Level
Ohio · updated daily from the U.S. Geological Survey
871.30 ft
Grand Lake St Marys is current reading available and rising (+0.85 ft in the last 7 days).
Change since yesterday: +0.11 ft
Reading as of 2026-08-15
Where Grand Lake St Marys sits historically
Today's level compared with every reading in our 0.3-year record for this lake.
Since yesterday
+0.11 ft
7-day change
+0.85 ft
30-day change
+0.67 ft
1-year change
— ft
Last 30 days
Last 12 months
Grand Lake St Marys records and averages
| Current level | 871.30 ft |
|---|---|
| Record high | 871.3 ft (2026-08-15) |
| Record low | 870.43 ft (2026-08-10) |
| Average of all readings | 870.85 ft |
| Data span | 0.3 years (121 readings) |
Frequently asked questions
Is Grand Lake St Marys full right now?
As of 2026-08-15, Grand Lake St Marys sits at 871.30 ft, which is current reading available.Over the past 30 days the level has risen 0.67 ft.
What is the water level at Grand Lake St Marys today?
The most recent reading is 871.30 ft (2026-08-15), sourced from the U.S. Geological Survey. Readings on this page refresh automatically as the agency publishes new data.
What is the highest Grand Lake St Marys has ever been?
The highest level in our records is 871.3 ft on 2026-08-15. The lowest is 870.43 ft on 2026-08-10. Our record covers about 0.3 years of readings.
Why is Grand Lake St Marys changing right now?
Reservoir levels move for four main reasons: rainfall and runoff into the basin, releases through the dam for downstream water supply, power generation or flood control, evaporation during hot months, and seasonal drawdown schedules set by the operating agency. Grand Lake St Marys has risen 0.67 ft over the past 30 days. For the operational reason on any given week, check the U.S. Geological Survey directly.
How much has Grand Lake St Marys changed over the past year?
Year-over-year comparison is not available for this lake yet. The full-history chart above covers 0.3 years, with a record high of 871.3 ft and a record low of 870.43 ft.
Nearby lakes in Ohio
Source: the U.S. Geological Survey. Readings are provisional and subject to revision by the publishing agency. All Ohio lake levels.